Filter bank multicarrier spread spectrum (FB-MC-SS) methods have previously been used for communication in harsh environments. In FB-MC-SS methods, each data symbol may be spread over N spectrally disjoint subcarrier frequency bands before transmission. At the receiver, a maximum ratio combiner (MRC) may combine the demodulated signals from different subcarrier bands to increase the signal-to-interference-plus-noise ratio (SINR) at the combiner output.
Assuming the receiver has already identified the presence of a data packet and has obtained the timing phase of the middle point of the received data symbols, methods have been adopted to measure the SINR at each subcarrier band and accordingly calculate the MRC coefficients. For example, method of performing these tasks has been described Haddidin et al., An underlay communication channel for 5G cognitive mesh networks: Packet design, implementation, analysis, and experimental results, IEEE International Conference on Communications (ICC) (2016). The receiver structure presented by Haddidin et al. can operate at some negative SINR, but may fail if part of the frequency band is corrupted by a high level of interference. Under this condition, the receiver may fail to detect the packet and/or identify the symbol timing phase, hence cannot operate successfully. In other words, in harsh environments, packet detection and symbol timing phase estimation are receiver bottle-necks that have not been addressed in prior solutions known to the inventors. Thus, the inventors have identified a need to address this limitation of FB-MC-SS communication methods.